What is Traceroute: What Does it Do & How Does It Work?

Last Updated : 23 Jul, 2025

Traceroute is a network diagnostic tool used to track the path that data packets take from one computer to another across a network (like the internet). It helps in determining the route and measuring the transit delays of packets over the internet. It's especially useful for identifying network issues such as slow response times, network congestion, or routing problems.

In simple terms, Traceroute shows you the path your data takes to reach its destination and the time it takes for each step of the journey.

What-is-Traceroute
What is Traceroute

What is Traceroute or Tracert?

Traceroute (or Tracert on Windows) is a network diagnostic tool used to track the route that data packets take as they travel from one computer to another across an IP network, such as the Internet. It helps users visualize the path that data follows, the intermediate points (or hops) it passes through, and the time taken for each hop to reach its destination. The tool is often used to identify network problems, such as latency, bottlenecks, and where packet loss or delays occur along the route.

What Does Traceroute Do?

Traceroute serves several key purposes in network management:

  1. Path Discovery: It reveals the route taken by packets to reach a destination, showing each intermediate device (router) along the way.
  2. Latency Measurement: Traceroute measures the time taken for packets to travel to each hop, helping to identify delays in the network.
  3. Network Troubleshooting: By pinpointing where packets are being delayed or dropped, Traceroute assists network administrators in diagnosing connectivity issues.
  4. Performance Analysis: It provides insights into the performance of the network, allowing for optimization and improvements.

How Does Traceroute Work?

Traceroute operates by sending a series of Internet Control Message Protocol (ICMP) Echo Request packets (or UDP packets, depending on the implementation) to the target destination. Here’s a step-by-step breakdown of how it works:

  • TTL (Time to Live) Field: Each packet sent by Traceroute has a TTL value, which determines how many hops (routers) the packet can traverse before being discarded. The initial TTL value is set to 1.
  • Packet Sending: The first packet is sent to the destination with a TTL of 1. When this packet reaches the first router, the router decrements the TTL by 1. Since the TTL reaches 0, the router discards the packet and sends back an ICMP Time Exceeded message to the source.
  • Incrementing TTL: Traceroute then sends another packet with a TTL of 2. This packet reaches the first router, which decrements the TTL to 1 and forwards it to the next router. The second router then decrements the TTL to 0, discards the packet, and sends back another ICMP Time Exceeded message.
  • Repeating the Process: This process continues, incrementing the TTL with each packet sent, until the packets reach the destination or a maximum TTL value is reached.
  • Collecting Results: For each hop, Traceroute records the round-trip time (RTT) for the packet to reach the router and return the ICMP message. This information is displayed to the user, showing the IP address of each hop and the time taken.

Important Reads related to Traceroute

How To Read A Traceroute Report

  1. Hop Number: The number of the router or device in the sequence of hops (e.g., 1st hop, 2nd hop, etc.).
  2. IP Address: The IP address of the router or device handling the packet at that hop.
  3. Round-Trip Time (RTT): The time it took for a packet to reach that hop and return to the source. Traceroute typically measures three RTTs per hop.
  4. Timeout or Asterisk (*): If a hop is not responding, it will show as * * * indicating a timeout or refusal to respond to the traceroute request.

Why is Traceroute Useful

Traceroute is helpful in several ways. It allows network administrators, IT professionals, and even regular users to diagnose problems with their internet connection or the websites they are trying to reach. Here’s why traceroute is so valuable:

  1. Diagnosing Slow Internet: If you’re having trouble with slow internet or trouble accessing a website, traceroute can show where the problem is. Is it your local network, your internet service provider (ISP), or a problem on the website's server? Traceroute helps you figure that out.
  2. Identifying Network Problems: Traceroute helps you identify exactly where in the path the data gets slowed down. For example, if it’s taking too long to reach a certain router in the path, you’ll see that in the results. This can tell you if there’s a problem with a specific router or part of the network.
  3. Visualizing the Network Path: If you’re curious about how data travels, traceroute gives you a clear view of the route your data takes across different networks, cities, or even countries.

How to Run Traceroute?

On Windows (using Tracert):

Open Command Prompt (cmd) by pressing Windows + R, typing cmd, and pressing Enter > Type the following command and press Enter:

tracert google.com

Replace google.com with any domain or IP address you want to trace.

On macOS or Linux (using Traceroute):

Open the Terminal > Type the following command:

traceroute google.com

You may need to install traceroute first on Linux using a package manager (e.g., sudo apt-get install traceroute for Ubuntu).

Traceroute Output Example

Here is what a typical Traceroute output might look like:

traceroute to google.com (142.250.190.78), 30 hops max, 60 byte packets

1 192.168.1.1 (192.168.1.1) 1.111 ms 0.839 ms 0.712 ms

2 10.50.1.1 (10.50.1.1) 5.458 ms 5.283 ms 5.089 ms

3 72.14.205.69 (72.14.205.69) 20.274 ms 21.180 ms 20.411 ms

4 216.239.46.32 (216.239.46.32) 21.634 ms 22.473 ms 22.315 ms

5 108.177.98.133 (108.177.98.133) 15.927 ms 16.431 ms 16.903 ms

6 google.com (142.250.190.78) 16.723 ms 16.616 ms 16.701 ms

In this output:

  • 1, 2, 3, etc. are the hops (routers).
  • The IP addresses of the routers are displayed.
  • The time (in milliseconds) for each hop is shown. If the same hop has multiple times, it means the packet was sent multiple times, and these represent the round-trip time.
  • If a hop doesn't respond, it is marked with an asterisk *, indicating a timeout or that the router is not responding to ICMP requests.

Troubleshooting with Traceroute

Sometimes, when a website is slow or unreachable, traceroute can point out exactly where the issue lies. For example:

  • Long Delays: If you notice a large delay in one hop, like from your local router to the ISP’s router, the issue could be with your ISP (Internet Service Provider).
  • Timeouts: If any hops show “Request Timed Out,” it usually means a router or server is not responding, which might be due to a configuration issue or congestion.
  • Network Congestion: High response times at one particular hop can indicate network congestion or a bottleneck at that router, which can slow down the entire connection.

Example of Traceroute Results

Let’s imagine you're trying to visit amazon.com, and you’re using traceroute to see how data gets from your computer to their servers. The output might look like this

1  <1 ms  <1 ms  <1 ms  router.local
2   25 ms  24 ms  23 ms  isp-gateway.local
3   50 ms  51 ms  52 ms  amazon-router-ny.local
4   100 ms 101 ms 102 ms  amazon.com

From this output, you can see that there are no timeouts, and the times gradually increase. If there had been any high latency or timeouts, you would know where to look for the problem.

Limitations of Traceroute

  1. Blocked by Firewalls: Some routers or firewalls block ICMP packets (used by Traceroute), leading to incomplete results or timeouts in the output.
  2. Limited to Path Visibility: Traceroute only shows the visible route from your source to the destination. It might not reveal private network routing or issues that are outside the public internet path.
  3. False Positives: Sometimes, routers or devices will intentionally not respond to ICMP requests (for security reasons), which can result in incomplete or misleading output.
  4. Not Always Accurate for Latency: While Traceroute shows the round-trip time, this might not fully represent the actual latency perceived by the user. Latency can also be caused by congestion or other external factors not visible in the Traceroute results.

Conclusion

Traceroute is an essential tool for network administrators and engineers, providing critical information about the paths data packets take across networks. By understanding how Traceroute works and utilizing its capabilities, users can effectively troubleshoot network issues, analyze performance, and ensure optimal connectivity.

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